A proximity service between user equipments (Device to Device Proximity Service, D2D ProSe for short for short hereinafter) has become a research subject of a 3GPP LTE system Rel.12 system, and is supported in systems starting from the Rel.12 system. Because the LTE system is widely applied, a physical layer of the LTE system may be used to provide user equipment directly connected service, which may not only enrich a service range of the LTE system, but also enable user equipment directly connected (Device to Device, D2D for short hereinafter) application to be used by more users. According to ranges, D2D communication services may be classified into long-range communication services, middle-range communication services, and short-range communication services. A long-range communication service requires that a transmit power of a UE should be high, a short-range communication service requires that the transmit power of the UE should be low, and a middle-range communication service requires that the transmit power of the UE should be between the foregoing two power.
In order that better D2D communication quality can be provided for a user and that a power for sending a D2D signal by a user equipment (User Equipment, UE for short hereinafter) is prevented from exceeding a maximum transmit power allowed by the UE, it is necessary to control the transmit power when the UE sends the D2D signal. However, open-loop power control and closed-loop power control in the prior art are not suitable for direct use in a D2D communication system. For example, a long-range communication service is initiated by the UE, but the transmit power of the UE controlled by means of semi-static or static parameter configuration in the prior art is a low power, and therefore, a communication range of the UE cannot be ensured.